Production of



UNITED STATES PATENT OFFICE PRODUCTION OF 3- AND 4-CYANO- PYRIDINES John V. Scudi, Bronx, and Anthony F. Moschetto, Yonkers, N. 2., and George Mayurnik, Garfield,

N. J., assignors to Nepera. Chemical Co. Inc., Yonkers, N. Y., a corporation of New York No Drawing. Application September 25, 1951, Serial No. 248,268

5 Claims. (Cl. 260294.9)

l 2 This invention relates to the produc ion o of the vaporizer is kept at 200 C. to 400 C. and cyanopyridines and particularly to the producf the reactor is about 275 C. to 450 C. The

tion of 3- and i-cyanopyridines from pyridine exit gases from the reactor are passed through carboxylic acids having a carboxyl group in the a condenser, where they are cooled, and the 8 or 7 position, or in other words, having a carcondensibles collected in an ice-water cooled boxyl group attached to a carbon atom nonreceiver. After the reaction is stopped, the conadjacent to the nitrogen atom. denser is washed into the receiver with ethyl Of the above two cyanopyridines, S-cyanopyriether and the ether and water layers are sepadine is the more important one and is produced rated. The ether layer, which contains the at present commercially from 3-pyridine sulfonic 10 cyanopyridine in solution, may then be separated acid. The cyanopyridines, or nitriles, are used and dried with anhydrous sodium sulfate and for the direct production of the corresponding then distilled to recover the cyanopyridine. amides. They are, however, also important as For catalyst in the reactor we have employed intermediates for other syntheses. various dehydrating catalysts. Most of these are We have found that we can produce in a concommercially available and may be used in form venient way, 3- or l-cyanopyridines, or mixture of pellets or deposited on porous material like thereof, in the vapor phase by vaporizing the pumice, clay chips and the like. Of the comcorresponding pyridine carboxylic acids in a 'mercial dehydrating catalyst we use alumina, stream of ammonia and passing the mixtureover vanadium on alumina, vanadium on pumice, sila dehydrating catalyst, such as alumina, silica ica gel, activated carbon, but other dehydrating gel, etc. Z-pyridine carboxylic acid does not catalysts like thorium oxide, aluminum phosform Z-cyanopyridine when so treated. It will phate and others may be used also. be deCarbOXylated and py is e resultin We prefer to carry out our invention at atmosproduct. 2-,3-, and 2-,5-pyridine dicarboxylic pheric pressure, but it may be carried out at acids also decarboxylate in the 2-position and 5 superatmospheric pressure or partially reduced result in 3-cyanopyridines. pressure. In the last mentioned case, the suc- The probable equation of the reaction is the tion is applied on the receiving vessel. following: Having so described our invention, the fol- COOH ON lowing are several illustrative examples of the preferred procedures of carrying out our invention, which are given for illustration and not for limitation.

N N Example 1 A convenient manner of carrying out our in- The reaction was carried out in the equipment vention is to use a 1 inch, jacketed, stainless described above. The reactor tube was filled steel pipe or tube filled half way with glass beads with commercial alumina as catalyst and was or similar material, as the vaporizer. The jacket maintained at 350 C. 35 grams of nicotinic may be filled with a molten salt bath mixture acid (3-pyridine carboxylic acid) per hour was or other heat transfer agent, heated electrically, fed through the valve into the vaporizer in apor otherwise, to the desired temperature. The proximately equal quantities at fifteen minute solid pyridine carboxylic acids are introduced by intervals, while the vaporizer was maintained at a valve arrangement on the top, at definite in- 250C. Also, 55 grams per hour ofanhydrous tervals. Anhydrous ammonia is passed into the ammonia gas preheated to about 325 C. was fed vaporizer near the top, after being measured in into the same vaporizer. The resulting vapors a rotameter. The ammonia used should be at were passed into the hot reactor and the exit least equimolecular quantity, but the use of an gases cooled in the condenser and the product excess appears to be desirable, preferably subcollected in the ice-water cooled receiver. When stantially 2 or 3 times the weight of the acid the reaction was stopped, the condenser was used. The gases from the vaporizer are conwashed With ethyl ether into the receiver. The ducted to the top of a reactor tube which may aqueous layer was separated and the ether from also be made from a 1 inch stainless steel pipe. the solution, after drying with anhydrous sodium The reactor tube is packed with the catalyst and sulfate and filtering, was distilled off. The resiits temperature is maintained in a similar mandue was distilled in vacuum. The product was ner as that of the vaporizer. The temperature S-cyanopyridine, as determined by its melting 3 point and its mixed melting point with a known sample of this material. The yield obtained was 88% of the theoretical.

Example 2 The reaction was repeated as in Example 1, using commercial silica gel as catalyst in the reactor. 15 grams of nicontinic acid and 27 grams of anhydrous ammonia were passed into the reactor hourly. The temperature of both the vaporizer and reactor was maintained at 375 C. The product was worked up as in Example 1. Th yield of B-cyanopyridine was 68%.

Example 3 The reaction was repeated using activated carbon as catalyst. The same amount of nicotinic acid, and anhydrous ammonia were used as in Example 2. The temperatures on both tubes were maintained at 375 .C. The yield of 3-cyanopyridine in this case was 21 Example 4 Using the same amount of material and temperatures as in Example 3 with vanadium on pumice as catalyst, the yield of B-cyanopyridine obtained was 25 Example 5 In this example, 15 grams of quinolinic acid (2,3-pyridine dicarboxylic acid) was fed hourly into the reactor with 54 grams of anhydrous ammonia using commercial alumina as catalyst. The temperature was maintained at 375 C. in both vaporizer and reactor. The quinolinic acid decarboxylated in the 2-position and the product obtained was 3-cyanopyridine.

Example 6 In this example, 25 grams oi'isocinchomeronic acid (2,5-pyridine dicarhoxylic acid) was fed hourly into the reactor with 55 grams of anhydrous ammonia using commercial alumina as catalyst. The temperature was maintained at 300 C. on the vaporizer and at 375 C. on the re actor. The isocinchomeronic acid decarboxylated in the 2-position and the product obtained was B-cyanopyridine.

Example 7 The vaporizer was charged with 6.1 grams oi isonicotinic acid (l-pyridine carboxylic acid) and 13 grams of anhydrous ammonia passed through while the temperature in the vaporizer was kept about 250-320 0. Commercial vanadium on alumina was used as catalyst in the reactor which i Was heated to 350 C. The experiment was worked up as in the previous examples and the product obtained was -cyanopyridine.

Having so described our invention, we do not limit ourselves to the specifically mentioned times, temperatures, quantities, chemicals or steps of procedure, a these are given simply to clearly describe Our invention as set forth in our specification and claims, and they may be varied without going beyond the scope of our invention.

What we claim is:

1. The process of producing 3-, and 4cyano-= pyridines comprising the steps of vaporizing pyridine carboxylic acids selected from the group consisting of a pyridine carboxylic acid having a carboxy group in beta-position and a pyridine carboxylic acid having a carboxy group in gamma-position, between the temperatures of 200 to 400 C., passing the vapors with an excess. substantially 2 to 3 times the weight of the acid used, of anhydrous ammonia through a bed of dehydrating catalyst selected from the members of a group consisting of alumina, silica gel, vanadium, activated carbon, vanadium on alumina and vanadium on pumice, said bed of catalyst being heated to a temperature of 275 to 450 C.. collecting the cyanopyridine formed by condensation and purifying the product by distilling under reduced pressure.

2. The process of producing B-cyanopyridine comprising the step of passing the vapors of quinolinic acid and anhydrous ammonia through a bed of a dehydration catalyst selected from the group consisting of alumina, silica gel, vanadium, activated carbon, vanadium on alumina and vanadium on pumice, at an elevated temperature of 275 to 450 C. and decarboxylating the 2- carboxy group in the process.

3. The process of producing 3-cyan6pyridine comprising the step of passing the vapors of 2,5-pyridine dicarboxylic acid and anhydrous ammonia through a bed of a dehydration catalyst selected from the group consisting of alumina, silica gel, vanadium, activated carbon, vanadium on alumina and vanadium on pumice, at an elevated temperature of 275 to 450 C, and decarboxylating the 2-carboxy group in the procass.

4. The process of producing B-cyanopyridine comprising the step of passin the vapors of nicotinic acid and anhydrous ammonia through a bed of a dehydrating catalyst selected from the group consisting of alumina, silica gel, vanadium, activated carbon, vanadium on alumina and vanadium on pumice, at an elevated temperature of 275 to 450 C.

5. The process of producing 4-cyanopyridine comprising the step of passing the vapors of isonicotinic acid and anhydrous ammonia through a bed of a dehydrating catalyst selected from the group consisting of alumina, silica gel, vanadium, activated carbon, vanadium on alumina and vanadium on pumice, at an elevated temperature of 275 to 450 C.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,149,280 Deem ct a1. Mar. 7, 1939 2,200,734 Arnold et a1. May 14, 1940 2,412,749 Pike et a1; Dec. 17, 1946 2,427,400 Garbo Sept. 16, 1947 2,d37,933 Cislak et al Mar. 16, 1948 2,510,605 Porter et al. June 6, 1950 

1. THE PROCESS OF PRODUCING 3-, AND 4-CYANOPYRIDINES COMPRISING THE STEPS OF VAPORIZING PYRIDINE CARBOXYLIC ACIDS SELECTED FROM THE GROUP CONSISTING OF A PYRIDINE CARBOXYLIC ACID HAVING A CARBOXY GROUP IN BETA-POSITION AND A PYRIDINE CARBOXYLIC ACID HAVING A CARBOXY GROUP IN GAMMA-POSITION, BETWEEN THE TEMPERATURES OF 200* TO 400* C., PASSING THE VAPORS WITH AN EXCESS. SUBSTANTIALLY 2 TO 3 TIMES THE WEIGHT OF THE ACID USED, OF ANHYDROUS AMMONIA THROUGH A BED OF DEHYDRATING CATALYST SELECTED FROM THE MEMBER OF A GROUP CONSISTING OF ALUMINA, SILICA GEL, VANADIUM, ACTIVATED CARBON, VANADIUM ON ALUMINA AND VANADIUM ON PUMICE, SAID BED OF CATALYST BEING HEATED TO A TEMPERATURE OF 275* TO 450* C., COLLECTING THE CYANOPYRIDINE FORMED BY CONDENSATION AND PURIFYING THE PRODUCT BY DISTILLING UNDER REDUCED PRESSURE. 